Disposable absorbent articles, including disposable diapers, sanitary protection products, training pants, and adult incontinent products, typically include a so-called top sheet or facing layer positioned for contact with the user. This component of an absorbent article is foraminous in nature, such as by aperturing of a plastic film, or by virtue of the fibrous nature of a nonwoven fabric, whereby liquid introduced into the article can pass through the facing layer for retention in an associated absorbent structure.
Because it is generally preferred that the facing layer of an absorbent article remain dry-feeling, even after use of the article, formation of facing layer material from polymers has been generally preferred. However, such polymeric material, by nature, is ordinarily hydrophobic. Accordingly, wetting agents in the form of surfactants are typically incorporated in or on the facing layer to promote transfer of liquid therethrough.
Internal wetting agents are sometimes blended, in pellet form, with the polymeric materials used to form facing layers, and thereby impart wettability in the resulting extrudate, whether in the form of fibers or apertured films. One such wetting agent consists of a fatty substance (glycerol and/or sorbitol) reacted with lauric acid, and is commercially available from Ciba Chemical under the name of “Atmer.” The resultant surfactant product is then compounded with a polyolefin resin in a predeteimined concentration. Heretofore, the common practice for compounding these wetting agents is to blend the maximum amount of surfactant in with a minimum amount of a carrier resin. Typically, the maximum fatty substance concentration used for this application has ranged from 15% to 17%, by weight, of the resultant compound.
Experience has shown that under certain conditions, use of additives such as described above can result in the formation of defects in the polymeric materials being formed, such as fiber breaks in spun-melt processes and holes in cast film. These defects are believed to result from the heterogeneous distribution of the fatty substance additives. Because such defects can preclude formation of commercially acceptable fabrics and films, the present invention is directed to an improved internal wetting agent that desirably acts to significantly abate the creation of such defects in polymeric fabrics and films.